Method for distributing wireless charge power for multiple wireless power receivers

ABSTRACT

One embodiment of the present invention is capable of providing a method for efficiently transmitting power for multiple wireless power receivers by distributing the power of the wireless power receivers as power which matches the respective wireless power receivers in accordance with demand power information from the multiple wireless power receivers.

TECHNICAL FIELD

Embodiments of the present invention relate to wireless charging, andmore particularly, to a method for distributing wireless charging powerto a plurality of wireless power receivers in a wireless chargingnetwork.

BACKGROUND ART

Recently, wireless charging technology or non-contact chargingtechnology has been developed and has been widely utilized in variouselectronic devices. The wireless charging technology is a system thatuses wireless power transmission and reception in which, for example,the battery of a mobile phone may be automatically charged by simplyplacing the mobile phone on a charging pad without connecting to aseparate charging connector. The wireless charging technology canenhance the waterproof function by wirelessly charging the electronicproducts, and can improve the portability of electronic equipmentbecause a wired charger is not necessary.

Among them, charging by using a resonance method is performed asfollows. When a wireless power receiver (e.g., a mobile terminal), whichrequires charging, is positioned on a wireless power transmitter (e.g.,a charging pad), which transmits wireless power, the wireless powertransmitter may charge the wireless power receiver. In the case where aplurality of wireless power receivers are placed in a charging area of asingle wireless power transmitter, there may be a difference between thepower that is necessary for respective wireless power receivers and thetransmission power, so respective wireless power receivers are requiredto be efficiently charged.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

As described above, the power required by the wireless power receivermay be different from the power that can be transmitted from thewireless power transmitter. However, wireless power receivers arecurrently charged without a separate setting according to the powersupply capability of the wireless power transmitter. However, thecharging efficiency may vary depending on various charging conditions,such as the features of the wireless power receiver, hardware design,the distance between the wireless power receiver and the wireless powertransmitter, or the charging position. Furthermore, in the case oftransmitting power to a plurality of wireless power receivers, it isnecessary to adjust and transmit the power for more efficient powertransmission.

Technical Solution

Therefore, the embodiment of the present invention provides a method forefficiently distributing the wireless charging power to a plurality ofwireless power receivers.

A method of distributing wireless charging power to a plurality ofwireless power receivers in a wireless power transmitter, according tothe embodiment of the present invention, may include: transmitting powerto the first wireless power receiver to then charge the same; receivingdemand power information of the second wireless power receiver;determining power redistribution for the first wireless power receiverand the second wireless receiver based on the demand power information;and transmitting the power according to the power redistribution to thefirst wireless power receiver and the second wireless receiver,respectively.

A wireless power transmitter for distributing wireless charging power toa plurality of wireless power receivers, according to the embodiment ofthe present invention, may include: a charging unit that transmits powerto the first wireless power receiver to then charge the same; acommunication unit that receives demand power information of the secondwireless power receiver; and a controller that controls the chargingunit to determine power redistribution for the first wireless powerreceiver and the second wireless receiver based on the demand powerinformation, and to transmit the power according to the powerredistribution to the first wireless power receiver and the secondwireless receiver, respectively.

Advantageous Effects

According to the embodiment of the present invention, the amount ofpower distribution for each wireless power receiver may be determined inconsideration of the states of a plurality of wireless power receiversand the wireless power transmitter so that the power can be efficientlytransmitted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram illustrating the overall operations of awireless charging system.

FIG. 2 is a block diagram of a wireless power transmitter and a wirelesspower receiver, according to the embodiment of the present invention.

FIG. 3 is a detailed block diagram of a wireless power transmitter and awireless power receiver, according to an embodiment of the presentinvention.

FIG. 4 is a flowchart illustrating the operation of the wireless powertransmitter and the wireless power receiver, according to an embodimentof the present invention.

FIG. 5 is a flowchart illustrating the operation of the wireless powertransmitter and the wireless power receiver, according to anotherembodiment of the present invention.

FIG. 6 is a graph showing the amount of power applied by the wirelesspower transmitter depending on a time axis.

FIG. 7 is a flowchart illustrating a control method of the wirelesspower transmitter, according to an embodiment of the present invention.

FIG. 8 is a graph showing the amount of power applied by the wirelesspower transmitter depending on a time axis, according to the embodimentof FIG. 7.

FIG. 9 is a flowchart illustrating a control method of the wirelesspower transmitter, according to an embodiment of the present invention.

FIG. 10 is a graph showing the amount of power applied by the wirelesspower transmitter depending on a time axis, according to the embodimentof FIG. 9.

FIG. 11 is a block diagram of the wireless power transmitter and thewireless power receiver, according to an embodiment of the presentinvention.

FIG. 12 is a view showing a power distribution method for a plurality ofwireless power receivers, according to the first embodiment of thepresent invention.

FIG. 13 is a view showing a power distribution method for a plurality ofwireless power receivers, according to the second embodiment of thepresent invention.

FIG. 14 is a view showing a power distribution method for a plurality ofwireless power receivers, according to the third embodiment of thepresent invention.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the preferred embodiment of the present invention will bedescribed in more detail with reference to the accompanying drawings. Itshould be noted that the same components of the drawings are designatedby the same reference numeral anywhere. In the following description ofthe present invention, a detailed description of known functions andconfigurations incorporated herein will be omitted when it may make thesubject matter of the present invention rather unclear.

The embodiment of the present invention may provide a method forefficiently transmitting power to a plurality of wireless powerreceivers by distributing the power of the wireless power receivers tobe suitable for respective wireless power receivers according to demandpower information in the plurality of wireless power receivers.

According to the wireless charging standard, in the resonance type ofwireless charging, the wireless power transmitter (Power TransmissionUnit; PTU) is connected to the wireless power receiver (Power ReceiveUnit; PRU) by communication, and thereafter, the PRU and the PTUexchange their static parameters through static signals in order tothereby transmit its own state to the other party.

In the embodiments of the present invention, a plurality of PRUs maytransmit limitation power information to the PTU, and then the PTU maymore effectively distribute the charging power to each PRU. At thistime, for example, a PRU dynamic signal may be used to transmit thelimitation power information from the PRU to the PTU, but the presentinvention is not limited thereto, and newly defined other signals orpredefined other signals may be used to transmit the same.

First, the concept of a wireless charging system, which can be appliedto the embodiment of the present invention, will be described withreference to FIG. 1 to FIG. 11.

FIG. 1 is a conceptual diagram illustrating the overall operations ofthe wireless charging system. As shown in FIG. 1, the wireless chargingsystem includes a wireless power transmitter 100 and one or morewireless power receivers 110-1, 110-2, and 110-n.

The wireless power transmitter 100 may wirelessly transmit the power1-1, 1-2, or 1-n to the one or more wireless power receivers 110-1,110-2, and 110-n. More specifically, the wireless power transmitter 100may wirelessly transmit the power 1-1, 1-2, or 1-n only to the wirelesspower receivers that have been verified through a predeterminedverification process.

The wireless power transmitter 100 may form electrical connections withthe wireless power receivers 110-1, 110-2, and 110-n. For example, thewireless power transmitter 100 may transmit the wireless power in theform of an electromagnetic wave to the wireless power receivers 110-1,110-2, and 110-n.

Meanwhile, the wireless power transmitter 100 may perform bilateralcommunication with the wireless power receivers 110-1, 110-2, and 110-n.Here, the wireless power transmitter 100 and the wireless powerreceivers 110-1, 110-2, and 110-n may process, or transmit/receive,packets 2-1, 2-2, and 2-n, which are comprised of predetermined frames.The aforementioned frames will be described later in more detail. Thewireless power receivers may be implemented by, in particular, mobilecommunication terminals, PDAs, PMPs, or smart phones.

The wireless power transmitter 100 may wirelessly provide power to aplurality of the wireless power receivers 110-1, 110-2, and 110-n. Forexample, the wireless power transmitter 100 may wirelessly transmitpower to a plurality of the wireless power receivers 110-1, 110-2, and110-n by a resonance method. In the case where the wireless powertransmitter 100 adopts the resonance method, the distance between thewireless power transmitter 100 and each of the plurality of wirelesspower receivers 110-1, 110-2, and 110-n, preferably, may be equal to, orless than, 30 m. In addition, in the case where the wireless powertransmitter 100 adopts an electromagnetic induction method, the distancebetween the power supply device 100 and each of the plurality ofwireless power receivers 110-1, 110-2, and 110-n, preferably, may beequal to, or less than, 10 cm.

The wireless power receivers 110-1, 110-2, and 110-n may receivewireless power from the wireless power transmitter 100 in order tothereby charge a battery. In addition, the wireless power receivers110-1, 110-2, and 110-n may transmit, to the wireless power transmitter100, a signal that requests the wireless power transmission, informationthat is necessary for the wireless power reception, state information ofthe wireless power receiver, or control information of the wirelesspower transmitter 100. The information on the transmission signal willbe described later in more detail.

In addition, the wireless power receivers 110-1, 110-2, and 110-n maytransmit, to the wireless power transmitter 100, a message indicatingthe charging state of each wireless power receiver.

The wireless power transmitter 100 may include display means, such as adisplay, in order to thereby display the state of each of the wirelesspower receivers 110-1, 110-2, and 110-n based on the message receivedfrom each of the wireless power receivers 110-1, 110-2, and 110-n.Furthermore, the wireless power transmitter 100 may display theestimated time remaining to complete the charging of each of thewireless power receivers 110-1, 110-2, and 110-n.

The wireless power transmitter 100 may transmit a control signal fordisabling the wireless charging function to each of the wireless powerreceivers 110-1, 110-2, and 110-n. The wireless power receivers, whichhave received the control signal of disabling the wireless chargingfunction from the wireless power transmitter 100, may disable thewireless charging function.

FIG. 2 is a block diagram of a wireless power transmitter and a wirelesspower receiver, according to the embodiment of the present invention.

As shown in FIG. 2, the wireless power transmitter 200 may include apower transmitting unit 211, a controller 212, and a communication unit213. In addition, the wireless power receiver 250 may include a powerreceiving unit 251, a controller 252, and a communication unit 253.

The power transmitting unit 211 may provide the power required by thewireless power transmitter 200, and may wirelessly provide the power tothe wireless power receiver 250. Here, the power transmitting unit 211may supply power in the form of an alternating current wave, or maysupply power in the form of a direct current wave that is converted intoan alternating current wave by an inverter to then be supplied in theform of an alternating current wave. The power transmitting unit 211 maybe implemented in the form of a built-in battery, or may be implementedin the form of a power receiving interface in order to thereby receivepower from the outside and in order to thereby supply the same to othercomponents. It may be understood by those skilled in the art that thepower transmitting unit 211 is not limited and any means, which canprovide power in an alternating current waveform, may be adopted as thesame.

Furthermore, the power transmitting unit 211 may provide the wirelesspower receiver 250 with an alternating current wave in the form of anelectromagnetic wave. The power transmitting unit 211 may furtherinclude a resonant circuit, and thus, it may transmit or receive apredetermined electromagnetic wave. If the power transmitting unit 211is implemented by the resonant circuit, the inductance (L) of the loopcoil of the resonant circuit may be variable. Meanwhile, it may beunderstood by those skilled in the art that the power transmitting unit211 is not limited and any means, which can transmit and receive anelectromagnetic wave, may be adopted as the same.

The controller 212 may control the overall operations of the wirelesspower transmitter 200. The controller 212 may control the overalloperations of the wireless power transmitter 200 by using algorithms,programs, or applications, which are read from a storage unit (notshown) for control. The controller 212 may be implemented in the form ofa CPU, a microprocessor, or a minicomputer. The detailed operation ofcontroller 212 will be described later in more detail.

The communication unit 213 may perform communication with the wirelesspower receiver 250 in a predetermined manner. The communication unit 213may perform communication with the communication unit 253 of thewireless power receiver 250 by using a scheme of NFC (near fieldcommunication), Zigbee communication, infrared communication, visiblelight communication, Bluetooth communication, or BLE (Bluetooth lowenergy). The communication unit 213 may use a CSMA/CA algorithm as well.Meanwhile, the aforementioned communication schemes are merelyexemplary, and the scope of the embodiments of the present invention isnot limited to a specific communication scheme performed by thecommunication unit 213.

Meanwhile, the communication unit 213 may transmit a signal forinformation on the wireless power transmitter 200. Here, thecommunication unit 213 may unicast, multicast, or broadcast signals.

In addition, the communication unit 213 may receive power informationfrom the wireless power receiver 250. Here, the power information maycontain at least one of: the capability of the wireless power receiver250; the battery percentage, the number of times that charging occurs,the amount of usage, the battery capacity, or the battery ratio.

In addition, the communication unit 213 may transmit a charging functioncontrol signal for controlling the charging function of the wirelesspower receiver 250. The charging function control signal may control thewireless power receiving unit 251 of a specific wireless power receiver250 to enable, or disable, the charging function. Alternatively, as willbe described later in more detail, the power information may containinformation, such as the leading-in of a wired charging terminal, theswitch from an SA mode into an NSA mode, and the release of an errorsituation.

The communication unit 213 may receive signals from another wirelesspower transmitter (not shown) as well as from the wireless powerreceiver 250. For example, the communication unit 213 may receive anotice signal from another wireless power transmitter.

Meanwhile, although the power transmitting unit 211 and thecommunication unit 213 are illustrated to be different hardware elementssuch that the wireless power transmitter 200 performs the out-band typeof communication in FIG. 2, this is only an example. In the presentinvention, the power transmitting unit 211 and the communication unit213 may be implemented as a single hardware element so that the wirelesspower transmitter 200 may perform the in-band type of communication.

The wireless power transmitter 200 and the wireless power receiver 250may transmit and receive various signals, and thus, the registration ofthe wireless power receiver 250 in a wireless power network, which ismanaged by the wireless power transmitter 200, and the chargingoperation through the transmission and reception of wireless power maybe performed. The operation above will be described later in moredetail.

FIG. 3 is a detailed block diagram of the wireless power transmitter andthe wireless power receiver, according to an embodiment of the presentinvention.

As shown in FIG. 3, the wireless power transmitter 200 may include apower transmitting unit 211, a controller and communication unit 212 and213, a driving unit 214, an amplifying unit 215, and a matching unit216. The wireless power receiver 250 may include a power receiving unit251, a controller and communication unit 252 and 253, a rectifying unit254, a DC/DC converter 255, a switching unit 256, and a load unit 257.

The driving unit 214 may output a direct current power of apredetermined voltage value. The voltage value of the direct currentpower, which is output from the driving unit 214, may be controlled bythe controller and communication unit 212 and 213.

The direct current outputted from the driving unit 214 may be outputtedto the amplifying unit 215. The amplifying unit 215 may amplify thedirect current with a predetermined gain. In addition, the amplifyingunit may convert the direct current power into an alternating current onthe basis of a signal, which is inputted from the controller andcommunication unit 212 and 213. According to this, the amplifying unit215 may output an alternating current power.

The matching unit 216 may perform impedance matching. For example, byadjusting the impedance viewed from the matching unit 216,high-efficient power or high power may be outputted. The matching unit216 may adjust the impedance based on the control of the controller andcommunication unit 212 and 213. The matching unit 216 may include atleast one of a coil or a capacitor. The controller and communicationunit 212 and 213 may control the connection state with at least one ofthe coil or the capacitor in order to thereby perform impedancematching.

The power transmitting unit 211 may transmit the inputted alternatingcurrent power to the power receiving unit 251. The power transmittingunit 211 and the power receiving unit 251 may be implemented to beresonant circuits having the same resonance frequency. For example, theresonant frequency may be determined to be 6.78 MHz.

Meanwhile, the controller and communication unit 212 and 213 maycommunicate with the controller and communication unit 252 and 253 ofthe wireless power receiver 250, and for example, they may performcommunication (WiFi, ZigBee, or BT/BLE) in a bilateral frequency of 2.4GHz.

Meanwhile, the power receiving unit 251 may receive charge power.

The rectifying unit 254 may rectify wireless power received by the powerreceiving unit 251 into a direct current form, and, for example, may beimplemented in the form of a bridge diode. The DC/DC converter 255 mayconvert the rectified power into the power of a predetermined gain. Forexample, the DC/DC converter 255 may convert the rectified power suchthat the voltage of the output terminal is 5V. Meanwhile, the minimumand maximum values of the voltage, which can be applied to the frontterminal of the DC/DC converter 255, may be pre-configured.

The switching unit 256 may connect the DC/DC converter 255 and the loadunit 257. The switching unit 256 may maintain the on/off state accordingto the control of the controller 252. The load unit 257 may store theconverted power, which is inputted from the DC/DC converter 255, whenthe switching unit 256 is in the on state.

FIG. 4 is a flowchart illustrating the operation of the wireless powertransmitter and the wireless power receiver, according to an embodimentof the present invention. As shown in FIG. 4, the wireless powertransmitter 400 may be applied with power (S401). When the power isapplied, the wireless power transmitter 400 may configure theenvironment (S402).

The wireless power transmitter 400 may enter a power saving mode (S403).In the power saving mode, the wireless power transmitter 400 may applyheterogeneous power beacons for detection in each cycle, which will bedescribed in more detail in FIG. 6. For example, as shown in FIG. 4, thewireless power transmitter 400 may apply power beacons 404 and 405 fordetection, and power values of the power beacons 404 and 405 fordetection may be different from each other. Some, or all, of the powerbeacons 404 and 405 for detection may have the amount of power to drivethe communication unit of the wireless power receiver 450. For example,the wireless power receiver 450 may drive the communication unit bysome, or all, of the power beacons 404 and 405 for detection in order tothereby communicate with the wireless power transmitter 400. At thistime, such a state may be referred to as a null state.

The wireless power transmitter 400 may detect a load change by theplacement of the wireless power receiver 450. The wireless powertransmitter 400 may enter a low power mode (S408). The low power modewill be described in more detail with reference to FIG. 6 as well.Meanwhile, the wireless power receiver 450 may drive the communicationunit based on the power received from the wireless power transmitter 400(S409).

The wireless power receiver 450 may transmit a wireless powertransmitter searching signal (PTU searching) to the wireless powertransmitter 400 (S410). The wireless power receiver 450 may transmit thewireless power transmitter searching signal by using an advertisementsignal based on BLE. The wireless power receiver 450 may periodicallytransmit the wireless power transmitter searching signal, and maytransmit the same until a response signal is received from the wirelesspower transmitter 400 or until a predetermined period of time expires.

When the wireless power transmitter searching signal is received fromthe wireless power receiver 450, the wireless power transmitter 400 maytransmit a response signal (PRU Response) (S411). Here, the responsesignal may form a connection between the wireless power transmitter 400and the wireless power receiver 450.

The wireless power receiver 450 may transmit a PRU static signal (S412).Here, the PRU static signal may be a signal indicating the state of thewireless power receiver 450.

Meanwhile, the PRU static signal may have a data structure as shown inTable 1.

TABLE 1 Field Octets Description Use Units Optional fields 1 Defineswhich optional Mandatory validity fields are populated PRU ID 2 ID ofPRU Mandatory PRU Category 1 Category of PRU Mandatory PRU Information/1 Capabilities of PRU (bit Mandatory Capabilities field) Hardware rev 1Revision of the PRU HW Mandatory Firmware rev 1 Revision of the PRU SWMandatory maximum power 1 Maximum power desired Mandatory mW*100 desiredby PRU VRECT_MIN_STATIC 2 VRECT_MIN(static, first Mandatory mV estimate)VRECT_HIGH_STATIC 2 VRECT_HIGH(static, Mandatory mV first estimate)VRECT_SET 2 VRECT_SET Mandatory mV ΔR1 value 2 Delta R1 caused by PRUOptional .01 ohms(assume tabletop PTU) RRX_IN value 2 RRX_IN valueMandatory Mohms Rectifier imped 1 Rectifier impedance Mandatory0~5(0~250).02 xform transformation x resolution Rectifier 1 Efficiencyof rectifier Mandatory 0-100%(0-255) efficiency

Therefore, the wireless power transmitter 400 may transmit a PTU staticsignal, which contains data fields as shown in Table 1, to the wirelesspower receiver (S413). The PTU static signal transmitted by the wirelesspower transmitter 400 may be a signal that indicates the capability ofthe wireless power transmitter 400.

When the wireless power transmitter 400 and the wireless power receiver450 transmit and receive the PRU static signal and the PTU staticsignal, the wireless power receiver 450 may periodically transmit a PRUdynamic signal (S414 and S415). The PRU dynamic signal may containinformation on one or more parameters that are measured in the wirelesspower receiver 450. For example, the PRU dynamic signal may containvoltage information of the rear end of the rectifying unit of thewireless power receiver 450. The state of the wireless power receiver450 may be named as a boot state (S407).

At this time, according to various embodiments of the present invention,a voltage value, which is readjusted depending on the situation, may becontained in the PRU static signal to then be transmitted so that theinitially configured voltage value can be readjusted to conform to thesituation by the PRU static signal.

Meanwhile, the wireless power transmitter 400 may enter a powertransmission mode (S416), and the wireless power transmitter 400 maytransmit a PRU control signal, which is a command signal, to allow thewireless power receiver 450 to perform the charging (S417). In the powertransmission mode, the wireless power transmitter 400 may transmitcharging power.

The PRU control signal transmitted by the wireless power transmitter 400may contain information for enabling/disabling the charging of thewireless power receiver 450 and permission information. The PRU controlsignal may be transmitted when the wireless power transmitter 400 is tochange the state of the wireless power receiver 450, or in apredetermined cycle (for example, in a cycle of 250 ms). The wirelesspower receiver 450 may change the configuration according to the PRUcontrol signal, and may transmit a PRU dynamic signal for reporting thestate of the wireless power receiver 450 (S418 and S419). The PRUdynamic signal transmitted by the wireless power receiver 450 maycontain at least one piece of voltage information, current information,or state and temperature information of the wireless power receiver. Atthis time, the state of the wireless power receiver 450 may be referredto as an on state.

Meanwhile, the PRU dynamic signal may have a data structure as shown inTable 2.

TABLE 2 Field Octets Description Use Units Optional fields 1 Defineswhich optional Mandatory fields are populated VRECT 2 Voltage at diodeoutput Mandatory mV IRECT 2 Current at diode output Mandatory mA VOUT 2Voltage at charge/battery port Optional mV IOUT 2 Current atcharge/battery port Optional mA Temperature 1 Temperature of PRUOptional Deg C. from −40 C. VRECT_MIN_DYN 2 VRECT_MIN_LIMIT(dynamicOptional mV value) VRECT_SET_DYN 2 Desired VRECT(dynamic value) OptionalmV VRECT_HIGH_DYN 2 VRECT_HIGH_LIMIT(dynamic Optional mV value) PRUalert 1 Warnings Mandatory Bit field

The PRU dynamic signal, as shown in Table 2, may contain at least oneof: optional field information; voltage information of the rear end ofthe rectifying unit of the wireless power receiver; current informationof the rear end of the rectifying unit of the wireless power receiver;voltage information of the rear end of the DC/DC converter of thewireless power receiver; current information of the rear end of theDC/DC converter of the wireless power receiver; temperature information;minimum voltage value information (VRECT_MIN_DYN) of the rear end of therectifying unit of the wireless power receiver; optimal voltage valueinformation (VRECT_SET_DYN) of the rear end of the rectifying unit ofthe wireless power receiver; maximum voltage value information(VRECT_HIGH_DYN) of the rear end of the rectifying unit of the wirelesspower receiver; or alert information (PRU alert).

Thus, as described above, one or more configured voltage values {e.g.,the minimum voltage value information (VRECT_MIN_DYN) of the rear end ofthe rectifying unit of the wireless power receiver, the optimal voltagevalue information (VRECT_SET_DYN) of the rear end of the rectifying unitof the wireless power receiver, or the maximum voltage value information(VRECT_HIGH_DYN) of the rear end of the rectifying unit of the wirelesspower receiver}, which are determined according to the situation, may becontained in the corresponding field of the PRU dynamic signal to thenbe transmitted. As described above, the PTU, which has received the PRUdynamic signal, adjusts the wireless charging voltage to be transmittedto each PRU with reference to the configured voltage values contained inthe PRU dynamic signal.

The alert information may be formed in a data structure as shown inTable 3 below.

TABLE 3 7 6 5 4 3 2 1 0 over over over charge TA transi- restart RFUvoltage current temper- complete detect tion request ature

The alert information, as shown in Table 3, may contain fields of overvoltage, over current, over temperature, charge complete, wired chargingterminal insertion detection (TA detect), SA mode/NSA mode transition,and restart request.

The wireless power receiver 450 may receive a PRU control signal inorder to thereby perform the charging. For example, if the wirelesspower transmitter 400 has enough power to charge the wireless powerreceiver 450, the wireless power transmitter 400 may transmit a PRUcontrol signal to enable the charging. Meanwhile, the PRU control signalmay be transmitted whenever the charging state is changed. The PRUcontrol signal, for example, may be transmitted every 250 ms, or may betransmitted when a parameter is changed. The PRU control signal may beconfigured to be transmitted within a predetermined threshold time (forexample, 1 second) even without the change in the parameters.

Meanwhile, the wireless power receiver 450 may detect the occurrence oferrors. The wireless power receiver 450 may transmit an alert signal tothe wireless power transmitter 400 (S420). The alert signal may betransmitted by using the PRU dynamic signal or the PRU alert signal. Forexample, the wireless power receiver 450 may reflect the errorconditions to the PRU alert field of Table 3, and may transmit the sameto the wireless power transmitter 400. Alternatively, the wireless powerreceiver 450 may transmit a single alert signal (e.g., the PRU alertsignal), which indicates the error conditions, to the wireless powertransmitter 400. When the alert signal is received, the wireless powertransmitter 400 may enter a latch fault mode (S422). The wireless powerreceiver 450 may enter the null state (S423).

FIG. 5 is a flowchart illustrating the operation of the wireless powertransmitter and the wireless power receiver, according to anotherembodiment of the present invention. The control method of FIG. 5 willbe described in more detail with reference to FIG. 6. FIG. 6 is a graphshowing the amount of power applied by the wireless power transmitterdepending on a time axis in the embodiment of FIG. 5.

As shown in FIG. 5, the wireless power transmitter may initiate theoperation (S501). In addition, the wireless power transmitter may resetthe initial configuration (S503). The wireless power transmitter mayenter a power saving mode (S505). Here, the power saving mode may be aperiod in which the wireless power transmitter applies heterogeneouspower with a different amount of power to the power transmitting unit.For example, it may be a period in which the wireless power transmitterapplies, to the power transmitting unit, the second detection power 601or 602 and the third detection power 611, 612, 613, 614, or 615 in FIG.6. Here, the wireless power transmitter may periodically apply thesecond detection power 601 or 602 in the second cycle for the secondperiod of time. The wireless power transmitter may periodically applythe third detection power 611, 612, 613, 614, or 615 in the third cyclefor the third period of time. Meanwhile, although the third detectionpower values 611, 612, 613, 614, and 615 are illustrated to be differentfrom each other, the third detection power values 611, 612, 613, 614,and 615 may be different, or may be the same.

For example, after outputting the third detection power 611, thewireless power transmitter may output the third detection power 612 ofthe same amount of power. As described above, in the case where thewireless power transmitter outputs the third detection power of the samevalue, the third detection power may have the amount of power that iscapable of detecting the smallest wireless power receiver (for example,the wireless power receiver of category 1).

On the contrary, after outputting the third detection power 611, thewireless power transmitter may output the third detection power 612,which is a different amount of power. As described above, in the casewhere the wireless power transmitter outputs the third detection powerof a different value, the third detection power may have an amount ofpower that is capable of detecting the wireless power receivers ofcategories 1 to 5. For example, the third detection power 611 may havean amount of power that is capable of detecting the wireless powerreceiver of category 5, and the third detection power 612 may have anamount of power that is capable of detecting the wireless power receiverof category 3. In addition, the third detection power 613 may have anamount of power that is capable of detecting the wireless power receiverof category 1.

Meanwhile, the second detection power 601 or 602 may drive the wirelesspower receiver. More specifically, the second detection power 601 or 602may have an amount of power that is capable of driving the controllerand the communication unit of the wireless power receiver.

The wireless power transmitter may apply, to the power receiving unit,the second detection power 601 or 602 and the third detection power 611,612, 613, 614, or 615 in the second cycle and in the third cycle,respectively. In the case where the wireless power receiver is placed onthe wireless power transmitter, the impedance viewed from one point ofthe wireless power transmitter may be changed. The wireless powertransmitter may detect a change in the impedance while applying thesecond detection power 601 or 602 and the third detection power 611,612, 613, 614, or 615. For example, the wireless power transmitter maydetect a change in the impedance while applying the third detectionpower 615. According to this, the wireless power transmitter may detectan object (S507). If no object is detected (S507—N), the wireless powertransmitter may maintain the power saving mode in which heterogeneouspower is periodically applied (S505).

Meanwhile, if the object is detected due to the change in the impedance(S507—Y), the wireless power transmitter may enter a low power mode.Here, the low power mode means a mode in which the wireless powertransmitter applies driving power that is capable of driving thecontroller and the communication unit of the wireless power receiver.For example, in FIG. 6, the wireless power transmitter may apply thedrive power 620 to the power transmitting unit. The wireless powerreceiver may receive the drive power 620 in order to thereby drive thecontroller and the communication unit. The wireless power receiver mayperform communication with the wireless power transmitter in apredetermined manner based on the drive power 620. For example, thewireless power receiver may transmit and receive data that is requiredfor the verification, and, based on the same, may join the wirelesspower network managed by the wireless power transmitter. However, when aforeign object other than the wireless power receiver is placed, thedata transmission and reception cannot be performed. Accordingly, thewireless power transmitter may determine whether or not the placedobject is a foreign object (S511). For example, if the wireless powertransmitter has failed to receive a response from the object for apredetermined period of time, the wireless power transmitter maydetermine the object to be a foreign object.

If the object is determined to be a foreign object (S511—Y), thewireless power transmitter may enter the latch fault mode (S513). On thecontrary, if the object is determined to not be a foreign object(S511—N), the wireless power transmitter may proceed with a registrationoperation (S519). For example, the wireless power transmitter mayperiodically apply the first power 631 to 634 of FIG. 6 in the firstcycle. The wireless power transmitter may detect a change in theimpedance while applying the first power. For example, if the foreignobject is collected (S515—Y), the wireless power transmitter may detectthe impedance change in order to thereby determine that the foreignobject has been collected. Alternatively, if the foreign object is notcollected (S515—N), the wireless power transmitter may not detect theimpedance change in order to thereby determine that the foreign objecthas not been collected. If the foreign object is not collected, thewireless power transmitter may output at least one of a lamp or an alertsound in order to thereby inform the user that the wireless powertransmitter is currently in the error state. According to this, thewireless power transmitter may include an output unit that outputs atleast one of a lamp and an alert sound.

If it is determined that a foreign object has not been collected(S515—N), the wireless power transmitter may maintain the latch faultmode (S513). Meanwhile, if it is determined that a foreign object hasbeen collected (S515—Y), the wireless power transmitter may re-enter thepower saving mode (S517). For example, the wireless power transmittermay apply the second power 651 or 652 and the third power 661 to 665 ofFIG. 5.

As described above, the wireless power transmitter may enter the latchfault mode if a foreign object other than the wireless power receiver isplaced. Furthermore, the wireless power transmitter may determinewhether or not a foreign object is collected on the basis of a change inthe impedance due to the power applied in the latch fault mode. That is,the criterion for entering the latch fault mode may be the placement ofa foreign object in the embodiment of FIGS. 5 and 6. Meanwhile, inaddition to the placement of a foreign object, the wireless powertransmitter may have various criteria for entering the latch fault mode.For example, the wireless power transmitter may be cross-connected withthe placed wireless power receiver, and in this case, the wireless powertransmitter may enter the latch fault mode.

According to this, in the case of the occurrence of thecross-connection, the wireless power transmitter is required to returnto the initial state, and the wireless power receiver is required to becollected. The wireless power transmitter may configure, as a criterionfor entering the latch fault mode, the cross-connection in which thewireless power receiver that is placed on another wireless powertransmitter joins the wireless power network. The operation of thewireless power transmitter in the case of the occurrence of errors,including the cross-connection, will be described with reference to FIG.7.

FIG. 7 is a flowchart illustrating a control method of the wirelesspower transmitter, according to an embodiment of the present invention.The control method of FIG. 7 will be described in more detail withreference to FIG. 8. FIG. 8 is a graph showing the amount of powerapplied by the wireless power transmitter depending on a time axis,according to the embodiment of FIG. 7.

The wireless power transmitter may initiate the operation (S701). Inaddition, the wireless power transmitter may reset the initialconfiguration (S703). The wireless power transmitter may enter a powersaving mode (S705). Here, the power saving mode may be a period in whichthe wireless power transmitter applies heterogeneous power with adifferent amount of power to the power transmitting unit. For example,it may be a period in which the wireless power transmitter applies, tothe power transmitting unit, the second detection power 801 or 802, andthe third detection power 811, 812, 813, 814, or 815 in FIG. 8. Here,the wireless power transmitter may periodically apply the seconddetection power 801 or 802 in the second cycle for the second period oftime. The wireless power transmitter may periodically apply the thirddetection power 811, 812, 813, 814, or 815 in the third cycle for thethird period of time. Meanwhile, although the third detection powervalues 811, 812, 813, 814, and 815 are illustrated to be different fromeach other, the third detection power values 811, 812, 813, 814, and 815may be different, or may be the same.

Meanwhile, the second detection power 801 or 802 may drive the wirelesspower receiver. More specifically, the second detection power 801 or 802may have an amount of power that is capable of driving the controllerand the communication unit of the wireless power receiver.

The wireless power transmitter may apply, to the power receiving unit,the second detection power 801 or 802 and the third detection power 811,812, 813, 814, or 815 in the second cycle and in the third cycle,respectively. In the case where the wireless power receiver is placed onthe wireless power transmitter, the impedance viewed from one point ofthe wireless power transmitter may be changed. The wireless powertransmitter may detect a change in the impedance while applying thesecond detection power 801 or 802 and the third detection power 811,812, 813, 814, or 815. For example, the wireless power transmitter maydetect a change in the impedance while applying the third detectionpower 815. According to this, the wireless power transmitter may detectan object (S707). If no object is detected (S707—N), the wireless powertransmitter may maintain the power saving mode in which heterogeneouspower is periodically applied (S705).

Meanwhile, if the object is detected due to the change in the impedance(S707—Y), the wireless power transmitter may enter a low power mode(S709). Here, the low power mode means a mode in which the wirelesspower transmitter applies driving power that is capable of driving thecontroller and the communication unit of the wireless power receiver.For example, in FIG. 8, the wireless power transmitter may apply thedrive power 820 to the power transmitting unit. The wireless powerreceiver may receive the drive power 820 in order to thereby drive thecontroller and the communication unit. The wireless power receiver mayperform communication with the wireless power transmitter in apredetermined manner based on the drive power 820. For example, thewireless power receiver may transmit and receive data that is requiredfor the verification, and, based on the same, may join the wirelesspower network managed by the wireless power transmitter.

Thereafter, the wireless power transmitter may enter a powertransmission mode for transmitting charging power (S711). For example,the wireless power transmitter may apply the charging power 821, asshown in FIG. 8, and the charging power may be transmitted to thewireless power receiver.

The wireless power transmitter may determine whether or not an erroroccurs in the power transmission mode. Here, the error may be theplacement of a foreign object on the wireless power transmitter, across-connection, over voltage, over current, over temperature, or thelike. The wireless power transmitter may include a sensing unit that canmeasure over voltage, over current, over temperature, or the like. Forexample, the wireless power transmitter may measure the voltage orcurrent of a reference point, and if the measured voltage or currentexceeds a threshold value, the wireless power transmitter may determinethat the criterion for over voltage or over current has been satisfied.Alternatively, the wireless power transmitter may include temperaturesensing means that measure the temperature of the reference point of thewireless power transmitter. If the temperature of the reference pointexceeds a threshold value, the wireless power transmitter may determinethat the criterion for over temperature has been satisfied.

Meanwhile, if the state is determined to be over voltage, over current,or over temperature according to the measurement of the temperature,voltage, or current, the wireless power transmitter may reduce thewireless charging power to a predetermined value in order to therebyprevent the over voltage, over current, or over temperature. At thistime, if the reduced voltage value of the wireless charging power isless than a configured minimum value {e.g., the minimum voltage value(V_(RECT) _(_) _(MIN) _(_) _(DYN)) of the rear end of the rectifyingunit of the wireless power receiver}, the wireless charging is stopped,so the configured voltage value may be readjusted according to theembodiment of the present invention.

Although the embodiment of FIG. 8 illustrates the error in which aforeign object is further placed on the wireless power transmitter, theerror is not limited thereto, and it may be easily understood by thoseskilled in the art that the wireless power transmitter may also operatein a similar manner in the case of a cross-connection, over voltage,over current, or over temperature.

If no error has occurred (S713—N), the wireless power transmitter maymaintain the power transmission mode (S711). Meanwhile, if an error hasoccurred (S713—Y), the wireless power transmitter may enter the latchfault mode (S715). For example, the wireless power transmitter may applythe first power 831 to 835 as shown in FIG. 8. Furthermore, the wirelesspower transmitter may output an error occurrence display that includesat least one of a lamp or an alert sound in the latch fault mode. If itis determined that the foreign object or the wireless power receiver hasnot been collected (S717—N), the wireless power transmitter may maintainthe latch fault mode (S715). Meanwhile, if it is determined that theforeign object or the wireless power receiver has been collected(S717—Y), the wireless power transmitter may enter the power saving modeagain (S719). For example, the wireless power transmitter may apply thesecond power 851 or 852 and the third power 861 to 865 of FIG. 8.

The operation has been described above, in which an error occurs whilethe wireless power transmitter transmits the charging power.Hereinafter, the operation will be described in which a plurality ofwireless power receivers on the wireless power transmitter receive thecharging power.

FIG. 9 is a flowchart illustrating a control method of the wirelesspower transmitter, according to an embodiment of the present invention.The control method of FIG. 9 will be described in more detail withreference to FIG. 10. FIG. 10 is a graph showing the amount of powerapplied by the wireless power transmitter depending on a time axis,according to the embodiment of FIG. 9.

As shown in FIG. 9, the wireless power transmitter may transmit chargingpower to the first wireless power receiver (S901). Furthermore, thewireless power transmitter may further allow the second wireless powerreceiver to join the wireless power network (S903). In addition, thewireless power transmitter may transmit charging power to the secondwireless power receiver (S905). More specifically, the wireless powertransmitter may apply a sum of charging power values required by thefirst wireless power receiver and the second wireless power receiver tothe power receiving unit.

FIG. 10 illustrates an embodiment for operation S901 to operation S905.For example, the wireless power transmitter may maintain the powersaving mode for applying the second detection power 1001 or 1002 and thethird detection power 1011 to 1015. Thereafter, the wireless powertransmitter may detect the first wireless power receiver, and may entera low power mode for maintaining the detection power 1020. Thereafter,the wireless power transmitter may enter a power transmission mode forapplying the first charging power 1030. The wireless power transmittermay detect the second wireless power receiver, and may let the secondwireless power receiver join the wireless power network. Furthermore,the wireless power transmitter may apply the second charging power 1040,which has an amount of power corresponding to a sum of power valuesrequired by the first wireless power receiver and the second wirelesspower receiver.

Referring back to FIG. 9, the wireless power transmitter may transmitthe charging power to both the first wireless power receiver and thesecond wireless power receiver (S905), and may detect the occurrence ofan error during the transmission (S907). Here, the error may be theplacement of a foreign object, a cross-connection, over voltage, overcurrent, or over temperature, as described above. If no error hasoccurred (S907—N), the wireless power transmitter may maintain theapplication of the second charging power 1040.

Meanwhile, if an error has occurred (S907—Y), the wireless powertransmitter may enter the latch fault mode (S909). For example, thewireless power transmitter may apply the first power 1051 to 1055 ofFIG. 10 in the first cycle. The wireless power transmitter may determinewhether or not all of the wireless power receiver and the secondwireless power receiver are collected (S911). For example, the wirelesspower transmitter may detect a change in the impedance while applyingthe first power 1051 to 1055. The wireless power transmitter maydetermine whether or not all of the wireless power receiver and thesecond wireless power receiver are collected based on whether or not theimpedance returns to an initial value.

If it is determined that all of the wireless power receiver and thesecond wireless power receiver have been collected (S911—Y), thewireless power transmitter may enter the power saving mode (S913). Forexample, the wireless power transmitter may apply the second detectionpower 1061 or 1062, and the third detection power 1071 to 1075 in thesecond cycle and in the third cycle, respectively, as shown in FIG. 10.

As described above, in the case of applying the charging power to aplurality of wireless power receivers, the wireless power transmittercan easily determine whether or not the wireless power receiver or theforeign object is collected upon the occurrence of errors.

FIG. 11 is a block diagram of the wireless power transmitter and thewireless power receiver, according to an embodiment of the presentinvention.

The wireless power transmitter 1100 may include a communication unit1110, a power amplifier (PA) 1120, and a resonator 1130. The wirelesspower receiver 1150 may include a communication unit 1151, anapplications processor (AP) 1152, a power management integrated circuit(PMIC) 1153, a wireless power integrated circuit (WPIC) 1154, aresonator 1155, an interface power management (IFPM) IC 1157, a traveladapter (TA) 1158, and a battery 1159.

The communication unit 1110 may perform communication with thecommunication unit 1151 based on a predetermined scheme (for example,the BLE scheme). For example, the communication unit 1151 of thewireless power receiver 1150 may transmit, to the communication unit1110 of the wireless power transmitter 1100, a PRU dynamic signal thathas a data structure shown in Table 2. As described above, the PRUdynamic signal may contain at least one piece of voltage information,current information, temperature information, or alert information, ofthe wireless power receiver 1150.

Based on the received PRU dynamic signal, an output power value from thepower amplifier 1120 may be adjusted. For example, if the wireless powerreceiver 1150 comes to a state of over voltage, over current, or overtemperature, the power value outputted from the power amplifier 1120 maybe reduced. Furthermore, if the voltage or current value of the wirelesspower receiver 1150 is less than a predetermined value, the power valueoutputted from the power amplifier 1120 may increase.

The charging power from the resonator 1130 may be wirelessly transmittedto the resonator 1155.

The wireless power integrated circuit 1154 may rectify the chargingpower received from resonator 1155, and may perform DC/DC converting.The wireless Power integrated circuit 1154 may drive the communicationunit 1151, or may charge the battery 1159 by using the converted power.

Meanwhile, a wired charging terminal may be inserted into the traveladapter 1158. A wired charging terminal, such as 30-pin connector or aUSB connector, may be inserted into the travel adapter 1158, and thetravel adapter 1158 may receive power supplied from the external powersource in order to thereby charge the battery 1159.

The interface power management integrated circuit 1157 may process thepower supplied from the wired charging terminal in order to therebyoutput the same to the battery 1159 and the power management integratedcircuit 1153.

The power manager integrated circuit 1153 may manage the wirelesslyreceived power, the wiredly received power, or the power applied to eachelement of the wireless power receiver 1150. The AP 1152 may receivepower information from the power manager integrated circuit 1153, andmay control the communication unit 1151 to transmit the PRU dynamicsignal for reporting the same.

Meanwhile, a node 1156, which is connected to the wireless powerintegrated circuit 1154, may be connected to the travel adapter 1158. Inthe case where a wired charging connector is inserted into the traveladapter 1158, a predetermined voltage (for example, 5V) may be appliedto the node 1156. The wireless power integrated circuit 1154 may monitorthe voltage applied to the node 1156 in order to thereby determinewhether or not the travel adapter is inserted.

As described above, the concept of the wireless charging system that maybe applied to the embodiment of the present invention has been describedwith reference to FIGS. 1 to 11. Hereinafter, a power distributionmethod for wireless charging, according to the embodiment of the presentinvention, will be described with reference to FIGS. 12 to 14.

FIG. 12 is a view showing a power distribution method for a plurality ofwireless power receivers, according to the first embodiment of thepresent invention.

FIG. 12 shows that the available charging power of the PTU 1200 is 10 Wand the maximum demand power of the PRU1 1210 is 7 W on the assumptionthat the efficiency of the resonator is 100%. When the PTU 1200 receivesa message that contains the maximum demand power information and thelimitation power information for the PRU1 1210, the PTU 1200 maytransmit the maximum demand power to the PRU1 1210 because the PTU 1200may provide the maximum demand power. In addition, the PTU 1200 maydeliver power transmission information to the PRU1 1210.

Subsequently, when the PRU2 1220 additionally joins, a connection may bemade by BLE ADV, and the PTU 1200 may receive, from the PRU2 1220, themaximum demand power information and the limitation power information ofthe PRU2 1220. The PTU 1200 may calculate the amount of power in orderto thereby determine power redistribution.

In this case, since the limitation power of each of the PRU1 1210 andPRU2 1220 is 5 W, even though the maximum demand power thereof is 7 W,the PTU 1200 may distribute a power of 5 W to each of the PRU1 1210 andPRU2 1220. Here, the maximum demand power represents the maximum powerthat can be received by the PRU, and the limitation power represents theminimum power that may be received by the PRU. For example, if thelimitation power of the PRU1 1210 is 5 W, it means that the PRU1 1210can receive all the power of 5 W to 7 W. Alternatively, the limitationpower may be configured step by step. For example, if the limitationpower of the PRU1 1210 is configured to be 10 W=>5 W=>3 W, it means thatthe PRU1 1210 may receive only the power corresponding to 10 W, 5 W, and3 W, respectively, from the PTU 1200.

According to this, when the PRU2 1220 newly joins, since the PTU 1200cannot transmit the maximum demand power of the PRU2 1220, the PTU 1200reduces the power for the PRU1 1210 from 10 W to 5 W. Accordingly, thePTU 1200 may instruct the PRU2 1220 to perform the charging at 5 W.Alternatively, the PTU 1200 may inform the PRU2 1220 of the availablepower based on the phased limitation power information of the PRU2 1220.According to this, the PRU2 1220 may adjust the limitation power.

The PTU 1200 may receive such a limitation power through a message thatis received from each of the PRU1 1210 and the PRU2 1220 afterconnecting to the PRU1 1210 and the PRU2 1220, respectively. The messagemay be sent in the preparation stage before transmitting power, and maycontain the requirements of the PRU. The requirements, for example, maycontain fixed values, such as maximum demand power information, a phasedlimitation power, or a fixed limitation power. The message may betransmitted through a communication channel between the PTU and the PRU.

In addition, the messages may also be transmitted to the PTU 1200 ifvarious situations that require the adjustment of the power occur in thePRU1 1210 and the PRU2 1220. The PTU 1200 may receive the message, andmay readjust the power to be a new value according to the situation (forexample, when the number of PRUs is changed, when a certain PRU is fullycharged, when the charging mode of the PRU is changed, or when thecharging is released). For example, if the temperature increasesexcessively, the current flows too much, or the voltage is excessivelyhigh during the charging, the PRU may transmit the readjusted valueV_(RECT) to the PTU in order to thereby control the charging power.

In addition, in another embodiment, if the charging mode of the PRUswitches from a CC (continuous current) mode to a CV (continuousvoltage) mode, or if the charging is complete in the CV mode, thetransmission of more power is not required, so the PTU may dynamicallyadjust the power value for each PRU in order to thereby redistribute thecharging power.

The PTU 1200 may transmit current charging power information to the PRU11210 and the PRU2 1220. For example, the PTU 1200 may provide the PRU11210 and the PRU2 1220 with information stating that the PTU 1200transmits 5 W of power to each of the PRU1 1210 and the PRU2 1220.

FIG. 13 is a view showing a power distribution method for a plurality ofwireless power receivers, according to the second embodiment of thepresent invention.

FIG. 13 shows an example in which the power adjustment is required dueto the CV charging completion, the CV mode switch, or the removal of thecharger in the PRU2 1320 while the available charging power of the PTU1200 is 10 W and the PRU1 1310 is being charged in the CC mode. Forexample, if the charging mode of the PRU2 1320 switches from the CC modeto the CV mode, or if the charging is complete in the CV mode, thetransmission of more power is not necessary. In addition, when the PRU21320 is out of the charging range of the PTU 1300, that is, if the PRU21320 is removed from the PTU 1300, the power transmission is notnecessary. When the power transmission to the PRU2 1320 is not necessaryaccording to such various cases, the PTU 1300 may recalculate thecharging supply power capability to then be supplied. According to this,the PTU 1300 may convert the limitation power, which has been suppliedto the PRU1 1310, to the maximum demand power to then be supplied. Forexample, provided that the maximum demand power of the PRU1 1310 is 7 Wand the limitation power thereof is 5 W, the PTU 1300 may increase thepower from 5 W, which has been supplied to charge the PRU1 1310, to 7 Win order to thereby perform the charging.

In this state, if the PRU additionally joins, the PTU 1300 may calculatethe amount of power. If the PTU 1300 determines that the PTU 1300 cannottransmit the limitation power required by the PRU that is being chargedby redistributing the power as a result of the calculation, the PTU 1300may reject the newly joining PRU. That is, the additionally joining PRUmay not be charged.

At this time, the method for converting the limitation power to themaximum demand power is as follows.

First, the PTU 1300 may transmit a load switch off command to the PRU11310. According to this, the PRU1 1310 turns off a load switch in orderto thereby perform resetting. Then, the PTU 1300 may control the powerwith respect to the PRU1 1310 again in order to thereby perform thecharging. Here, as the implementation issue of a PRU configurationalgorithm, in order to reduce a sudden change in the voltage of the PRU11310, the PRU1 1310 may be turned off first, and then the PRU2 may beturned on.

FIG. 14 is a view showing a power distribution method for a plurality ofwireless power receivers, according to the third embodiment of thepresent invention.

FIG. 14 shows an example in which: the available charging power of thePTU 1400 is 5 W; the maximum demand power of the PRU1 1410 is 7 W; andthe limitation power thereof is 5 W. In this case, even though theavailable charging power 5 W of the PTU 1400 is less than the maximumdemand power 7 W of the PRU1 1410, the charging can be performed becausethe available charging power of the PTU 1400 satisfies the limitationpower 5 W of the PRU1 1410.

According to this, if it is determined that the PTU 1400 cannot providethe maximum demand power of the PRU1 1410, the PTU 1400 may check thelimitation power of the PRU1 1410, and may inform of the available powerof the PTU 1400. Then, the PRU1 1410 may adjust the demand power. Inthis method of the PRU, for example, the PTU may adjust the settings, orthe PRU may set the demand power to then receive an input of thecharging current.

As described above, when the PTU receives, from the PRU, the limitationpower information and/or the reduced power information, the PTUdetermines the supply power to the PRU.

1. A method of distributing wireless charging power to a plurality ofwireless power receivers in a wireless power transmitter, the methodcomprising: transmitting power to the first wireless power receiver tothen charge the same; receiving demand power information of the secondwireless power receiver; determining power redistribution for the firstwireless power receiver and the second wireless receiver based on thedemand power information; and transmitting the power according to thepower redistribution to the first wireless power receiver and the secondwireless receiver, respectively.
 2. The method according to claim 1,wherein the demand power information contains maximum demand powerinformation and limitation power information.
 3. The method according toclaim 1, further comprising receiving the demand power information thatcontains maximum demand power information and limitation powerinformation of the first wireless power receiver before transmittingpower to the first wireless power receiver and charging the same.
 4. Themethod according to claim 1, wherein the determining of the powerredistribution comprises: determining whether or not to distribute thepower corresponding to the maximum demand power of the second wirelesspower receiver based on an available charging power of the wirelesspower transmitter; and distributing the power corresponding to thelimitation power of the second wireless power receiver if it isimpossible to distribute the power corresponding to the maximum demandpower of the second wireless power receiver.
 5. The method according toclaim 4, further comprising informing the second wireless power receiverof available power information of the wireless power transmitter inorder to thereby adjust the limitation power of the second wirelesspower receiver if it is impossible to distribute the power correspondingto the maximum demand power of the second wireless power receiver. 6.The method according to claim 5, further comprising receiving adjusteddemand power information from the second wireless power receiver.
 7. Themethod according to claim 1, further comprising recalculating the powerfor the first wireless power receiver and the second wireless receiverand supplying the same when the charging mode of at least one of thefirst wireless power receiver and the second wireless power receiver ischanged.
 8. The method according to claim 1, further comprisingtransmitting a load switch off command in order to switch the power forthe first wireless power receiver that is being charged to the maximumdemand power when the charging for the second wireless receiver is notnecessary.
 9. A wireless power transmitter for distributing wirelesscharging power to a plurality of wireless power receivers, the wirelesspower transmitter comprising: a charging unit that transmits power tothe first wireless power receiver to then charge the same; acommunication unit that receives demand power information of the secondwireless power receiver; and a controller that controls the chargingunit to determine power redistribution for the first wireless powerreceiver and the second wireless receiver based on the demand powerinformation, and to transmit the power according to the powerredistribution to the first wireless power receiver and the secondwireless receiver, respectively.
 10. The wireless power transmitteraccording to claim 9, wherein the demand power information containsmaximum demand power information and limitation power information. 11.The wireless power transmitter according to claim 9, wherein thecommunication unit receives the demand power information that containsmaximum demand power information and limitation power information of thefirst wireless power receiver before transmitting power to the firstwireless power receiver and charging the same.
 12. The wireless powertransmitter according to claim 9, wherein the controller determineswhether or not to distribute the power corresponding to the maximumdemand power of the second wireless power receiver based on an availablecharging power of the wireless power transmitter, and distributes thepower corresponding to the limitation power of the second wireless powerreceiver if it is impossible to distribute the power corresponding tothe maximum demand power of the second wireless power receiver.
 13. Thewireless power transmitter according to claim 12, wherein the controllercontrols the communication unit to inform the second wireless powerreceiver of available power information of the wireless powertransmitter in order to thereby adjust the limitation power of thesecond wireless power receiver if it is impossible to distribute thepower corresponding to the maximum demand power of the second wirelesspower receiver.
 14. The wireless power transmitter according to claim 9,wherein the controller recalculates the power for the first wirelesspower receiver and the second wireless receiver and supplies the samewhen the charging mode of at least one of the first wireless powerreceiver and the second wireless power receiver is changed.
 15. Thewireless power transmitter according to claim 9, wherein the controllercontrols the communication unit to transmit a load switch off command inorder to switch the power for the first wireless power receiver that isbeing charged to the maximum demand power when the charging for thesecond wireless receiver is not necessary.